A jack-up rig is a type of offshore platform consisting of legs (“spuds”) that can be lowered or raised vertically. A jack-up platform can be towed or is self propelled. Once at a chosen location, the legs are lowered vertically to rest on the sea floor. The bottom ends of the legs may be configured to penetrate the sea floor, or may be provided with pads to support themselves on the sea floor. Once the legs reach the sea floor and can no longer be lowered, the platform is lifted above the surface of the water such that the platform is no longer floating on the surface of the water, but is supported above the surface of the water by the legs.
A somewhat similar technology is used by barges that wish to remain stationary on the surface of the water while performing some type of work. In this type of vessel, a barge may consist of a plurality of spuds that are similarly driven vertically downward to support themselves from the sea floor. In this case, however, the vessel remains floating on the surface of the water while the spuds hold the vessel at a stationary location. While stationary, the vessel may perform various types of work. In some cases the barge is partially lifted by the spuds to further stabilize the barge, for example, excavator barges may be used to dredge a channel.